U.S. patent number 10,240,235 [Application Number 13/407,832] was granted by the patent office on 2019-03-26 for method and apparatus for depositing a material layer originating from process gas on a substrate wafer.
This patent grant is currently assigned to SILTRONIC AG. The grantee listed for this patent is Alois Aigner, Georg Brenninger, Christian Hager. Invention is credited to Alois Aigner, Georg Brenninger, Christian Hager.
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United States Patent |
10,240,235 |
Brenninger , et al. |
March 26, 2019 |
Method and apparatus for depositing a material layer originating
from process gas on a substrate wafer
Abstract
An apparatus for depositing a material layer originating from
process gas on a substrate wafer, contains: a reactor chamber
delimited by an upper dome, a lower dome, and a side wall; a
susceptor for holding the substrate wafer during the deposition of
the material layer; a preheating ring surrounding the susceptor; a
liner, on which the preheating ring is supported in a centered
position wherein a gap having a uniform width is present between
the preheating ring and the susceptor; and a spacer acting between
the liner and the preheating ring, the spacer keeping the
preheating ring in the centered position and providing a distance
.DELTA. between the preheating ring and the liner.
Inventors: |
Brenninger; Georg
(Oberbergkirchen, DE), Aigner; Alois (Marktl,
DE), Hager; Christian (Kastl, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Brenninger; Georg
Aigner; Alois
Hager; Christian |
Oberbergkirchen
Marktl
Kastl |
N/A
N/A
N/A |
DE
DE
DE |
|
|
Assignee: |
SILTRONIC AG (Munich,
DE)
|
Family
ID: |
45528629 |
Appl.
No.: |
13/407,832 |
Filed: |
February 29, 2012 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20120263875 A1 |
Oct 18, 2012 |
|
Foreign Application Priority Data
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|
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|
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Apr 18, 2011 [DE] |
|
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10 2011 007 632 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/6719 (20130101); C23C 16/4401 (20130101); C23C
16/4585 (20130101); H01L 21/68735 (20130101) |
Current International
Class: |
C23C
16/44 (20060101); H01L 21/67 (20060101); C23C
16/458 (20060101); H01L 21/687 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1529900 |
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Sep 2004 |
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CN |
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2002-141294 |
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May 2002 |
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JP |
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2003142411 |
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May 2003 |
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JP |
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2003-218039 |
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Jul 2003 |
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JP |
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2006049503 |
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Feb 2006 |
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JP |
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2006-66432 |
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Mar 2006 |
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JP |
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1998-081271 |
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Nov 1998 |
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KR |
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2007003172 |
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Jan 2007 |
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KR |
|
I258189 |
|
Jan 1992 |
|
TW |
|
2007050309 |
|
May 2007 |
|
WO |
|
Primary Examiner: Kendall; Benjamin
Attorney, Agent or Firm: Brooks Kushman P.C.
Claims
What is claimed is:
1. An apparatus for depositing a material layer originating from
process gas on a substrate wafer, comprising a reactor chamber,
which is delimited by an upper dome and a lower dome and a side
wall; a rotatable susceptor for holding the substrate wafer during
deposition of the material layer; a preheating ring surrounding the
susceptor, the preheating ring having a circular central opening
within which the rotatable susceptor rotates; a liner, on which the
preheating ring is supported in a centered position wherein a gap D
having a uniform width is present between the preheating ring and
the susceptor; and a spacer between the liner and the preheating
ring, the spacer keeping the preheating ring in a centered position
and providing a vertical distance .DELTA. between the preheating
ring and the liner, the spacer comprising balls embedded partly in
recesses in the preheating ring and partly in the liner, which
enable a relative radial movement between the preheating ring and
the liner due to thermal expansion, each ball lying in a elongated
recess extending in a radial direction.
2. The apparatus of claim 1, wherein the gap D has a uniform width
of not less than 0.1 mm and not more than 2 mm.
3. The apparatus of claim 1, wherein the distance between an outer
lateral boundary of the preheating ring and an inner lateral
boundary of the liner proximate the outer lateral boundary of the
preheating ring is not less than 0.1 mm and not more than 1.9
mm.
4. The apparatus of claim 2, wherein the distance between an outer
lateral boundary of the preheating ring and an inner lateral
boundary of the liner proximate the outer lateral boundary of the
preheating ring is not less than 0.1 mm and not more than 1.9
mm.
5. The apparatus of claim 1, wherein the vertical distance .DELTA.
between the preheating ring and the liner, in a region adjoining
the spacer is not less than 0.01 mm and not more than 2 mm.
6. The apparatus of claim 2, wherein the vertical distance .DELTA.
between the preheating ring and the liner, in a region adjoining
the spacer is not less than 0.01 mm and not more than 2 mm.
7. The apparatus of claim 3, wherein the vertical distance .DELTA.
between the preheating ring and the liner, in a region adjoining
the spacer is not less than 0.01 mm and not more than 2 mm.
8. The apparatus of claim 4, wherein the vertical distance .DELTA.
between the preheating ring and the liner, in a region adjoining
the spacer is not less than 0.01 mm and not more than 2 mm.
9. The apparatus of claim 1, wherein the balls are embedded in the
preheating ring and in the liner such that the balls are enabled to
move in a radial direction with respect to the center of the
susceptor.
10. The apparatus of claim 1, wherein the balls are located in
elongated recesses in the liner which extend radially from a
geometric center of the liner.
11. The apparatus of claim 1, wherein the balls are located in
elongated recesses in the preheating ring which extend radially
from a geometric center of the preheating ring.
12. The apparatus of claim 10, wherein the balls are located in
elongated recesses in the preheating ring which extend radially
from a geometric center of the preheating ring.
13. A method for depositing a material layer originating from
process gas on a substrate wafer, comprising directing the process
gas over a preheating ring to a substrate wafer held by a rotating
susceptor, in an apparatus of claim 1.
14. The method of claim 13, wherein the substrate wafer is held
during deposition in a centered position in which a gap D is
present between the preheating ring and the susceptor, the gap D
having a uniform width of not less than 0.1 mm and not more than 2
mm.
15. A method for depositing a material layer originating from
process gas on a substrate wafer, comprising directing the process
gas over a preheating ring to a substrate wafer held by a rotating
susceptor, in an apparatus of claim 2.
16. A method for depositing a material layer originating from
process gas on a substrate wafer, comprising directing the process
gas over a preheating ring to a substrate wafer held by a rotating
susceptor, in an apparatus of claim 3.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to German Patent Application No.
DE 102011007632.8 filed Apr. 18, 2011 which is herein incorporated
by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an apparatus for depositing a material
layer originating from process gas on a substrate wafer, and to a
method which uses said apparatus.
2. Background Art
The invention relates, in particular, to an apparatus for
depositing a material layer by chemical vapor deposition (CVD), for
example an apparatus for depositing an epitaxial layer on a
substrate wafer composed of a semiconductor material such as
silicon.
The basic construction of an apparatus for depositing a material
layer originating from process gas on a substrate wafer is known
and is evident, for example, from the description in WO 2007/050309
A1. Accordingly, such an apparatus comprises a reactor chamber,
which is delimited by an upper dome, a lower dome and a side wall.
Radiant heating systems are arranged above and below the reactor
chamber and, during the deposition of a material film, generate
enough heat in order that process gas directed over the substrate
wafer is activated and a material layer emerging from constituents
of the process gas forms on the surface of the substrate wafer. The
substrate wafer is held by a susceptor surrounded by a preheating
ring. The preheating ring lies on a liner, which is part of the
side wall of the reactor chamber. It has the function of supporting
the heating of process gas which is directed to the substrate
wafer. Integrated into the side wall are feed and outlet openings
for feeding in the process gas and for discharging waste gases
emerging therefrom.
JP2006049503 A2 discusses an apparatus used for depositing an
epitaxial film on a semiconductor wafer composed of silicon. The
apparatus has the basic construction described above and
furthermore has further feed and outlet openings integrated into
the side wall of the reactor chamber. The further feed and outlet
openings serve for feeding purging gas into that volume of the
reactor chamber which is present below the susceptor, and for
discharging the purging gas from this volume. In accordance with
the description in JP2006049503 A2, gaseous compounds can pass
through the gap between the preheating ring and the susceptor to
the growing epitaxial layer and alter the resistivity of the
epitaxial layer in the edge region of the semiconductor wafer. In
order to prevent this "autodoping" effect, JP2006049503 A2 proposes
covering the gap.
The inventors of the present invention have found that it is
necessary to deal with certain problems when using an apparatus
configured, in principle, like the apparatus described in WO
2007/050309 A1 or as described in JP2006049503 A2. This is because
there is the risk that the radial profile of the resistivity of an
epitaxially deposited layer composed of silicon, as considered over
the diameter of the substrate wafer, will become markedly
asymmetrical. Ideally, the profile is symmetrical or at least
almost symmetrical. Furthermore, it is expected that particles will
contaminate the deposited material layer to a comparatively high
extent.
SUMMARY OF THE INVENTION
Therefore, an object of the invention was to provide a solution
that avoids the problems described. These and other objects are
achieved by means of an apparatus for depositing a material layer
originating from process gas on a substrate wafer, the apparatus
comprising
a reactor chamber, which is delimited by an upper dome and a lower
dome and a side wall;
a susceptor for holding the substrate wafer during deposition of
the material layer;
a preheating ring surrounding the susceptor;
a liner, on which the preheating ring is supported in a centered
position in which a gap having a uniform width is present between
the preheating ring and the susceptor; and
a spacer acting between the liner and the preheating ring, said
spacer keeping the preheating ring in the centered position and
producing a distance .DELTA. between the preheating ring and the
liner.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a reactor chamber equipped with features according to
the invention.
FIG. 2 shows a plan view of a susceptor, a preheating ring and a
liner.
FIG. 3 is a detail view demonstrating features according to the
invention.
FIG. 4 shows the radial profile of resistivity of a layer of
silicon deposited epitaxially on a silicon wafer on the basis of an
example and a comparative example.
FIG. 5 and FIG. 6 show the result of particle measurements that
were performed on silicon wafers with an epitaxially deposited
layer of silicon.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
In the present invention, the susceptor and the substrate wafer are
rotated about their center during the deposition of a material
layer on the substrate wafer. The preheating ring, which is not
subjected to this rotary movement, should remain in a centered
position in the meantime. The inventors have surprisingly and
unexpectedly discovered that the problems previously described are
caused by virtue of the fact that the preheating ring leaves the
centered position, which it has assumed at the beginning of the
deposition process, in an uncontrolled manner during the course of
the process. The reason for this is a relative radial movement
between the preheating ring and the liner to thermal expansion,
which is attributable to different thermal expansion properties of
the material of the preheating ring and of the liner.
The displacement of the preheating ring on the liner has the
effect, firstly, that the width of the gap between the preheating
ring and the susceptor does not remain uniform, as is the case if
the preheating ring remained in the centered position. The width of
the gap starts to fluctuate along the periphery of the susceptor
during the course of the deposition process. The "autodoping"
effect is intensified where the gap is wider, because at these
locations more gas can pass through the gap to the growing material
layer.
The displacement of the preheating ring on the liner has the
effect, secondly, that particles arise on account of friction and
pass onto the deposited material layer and contaminate the latter.
The displacement of the preheating ring can even have the effect
that the preheating ring and the susceptor touch one another, which
augments the intensity of particle formation. For this reason, care
is taken to ensure that the gap between the preheating ring and the
susceptor has a width of at least 2 mm. However, such a width of
the gap promotes the "autodoping" effect previously described.
In order to avoid these problems, the claimed apparatus has a
spacer acting between the liner and the preheating ring, the spacer
keeping the preheating ring in the centered position independently
of its thermal expansion and independently of the thermal expansion
of the liner and producing a distance .DELTA. between the
preheating ring and the liner. In this way, direct contact between
the preheating ring and the liner is completely or almost
completely prevented. Owing to the lack of contact, a relative
radial movement between the preheating ring and the liner due to
thermal expansion during the deposition of the material film no
longer contributes to the formation of particles.
The susceptor and the preheating ring of the apparatus preferably
consists of a material described as suitable therefor in WO
2007/050309 A1, most preferably of silicon carbide. The preheating
ring preferably has a form described as suitable for it in WO
2007/050309 A1. Both these publications are incorporated herein by
reference.
The upper and lower domes of the apparatus and also the liner
consists of a material that is transmissive to IR radiation,
preferably of quartz.
In accordance with one embodiment of the invention, the spacer is
formed by suitable shaping of the preheating ring and of the liner.
Such shaping can consist, for example, in the preheating ring
having wedge-shaped projections that become located in grooves of
the liner, wherein the opening angles of the projections are
greater than those of the grooves.
In accordance with one preferred embodiment of the invention, the
spacer is formed by sliding balls that fix the preheating ring in
the centered position and at a specific distance above the liner.
The invention is explained in greater detail below on the basis of
the example of this embodiment and with reference to the
figures.
FIG. 1 shows a reactor chamber having the typical features of an
apparatus for depositing a material layer originating from process
gas on a substrate wafer and comprising features according to the
invention. The features illustrated include an upper dome 1, a
lower dome 2 and a side wall 3. The substrate wafer 4 is held by a
susceptor 5 surrounded by a preheating ring 6. The preheating ring
6 lies on a liner 7, which is part of the side wall 3 of the
reactor chamber. Sliding balls 8 distributed over the edge region
of the preheating ring function as a spacer between the preheating
ring 6 and the liner 7. The sliding balls preferably consist of
silicon carbide and their number is preferably 3 to 8, particularly
preferably 4.
FIG. 2 shows a plan view of the susceptor 5, the preheating ring 6
and the liner 7 and, in addition, the position of four sliding
balls 8 distributed on the circumference of the preheating ring
6.
As is evident from FIG. 3, the sliding balls 8 are partly embedded
in the preheating ring 6 and in the liner 7. The sliding balls 8 in
each case lie in a radially extending elongated hole 9, as a result
of which the preheating ring 6 is kept in the centered position
independently of its own thermal expansion and independently of the
thermal expansion of the liner 7 and has no contact with the liner
7 arranged underneath.
The distance .DELTA. between the preheating ring 6 and the liner 7
in the region adjoining the sliding balls 8 is preferably not less
than 0.01 mm and not more than 2 mm. If the distance is smaller,
the risk of particles arising on account of friction increases. If
the distance is larger, the risk increases that gas from the volume
below the susceptor will cause "autodoping" and/or deposit on the
reactor wall.
In order to counteract the "autodoping" effect, the gap D between
the preheating ring 6 and the susceptor 5 has a uniform width of
preferably not less than 0.1 mm and not more than 2 mm, more
preferably not more than 1 mm. If the gap D is smaller than 0.1 mm,
the preheating ring 6 could touch the susceptor 5 on account of
thermal expansion. If the gap D is larger than 2 mm, a significant
"autodoping" effect should be expected.
The distance d between an outer lateral boundary of the preheating
ring 6 and--lying opposite said boundary--an inner lateral boundary
of the liner 7 is preferably not less than 0.1 mm and not more than
1.9 mm. If the gap is smaller, the risk increases that the liner 7
and the preheating ring 6 will touch one another on account of
thermal expansion.
EXAMPLE AND COMPARATIVE EXAMPLE
The advantageous effect of the invention is evident if properties
such as the radial profile of the resistivity of the deposited
layer or the number of particles detected on the deposited layer
are compared in the case of semiconductor wafers composed of
silicon which are provided with an epitaxially deposited layer
composed of silicon.
FIG. 4 shows the radial profile of the resistivity of a layer of
silicon deposited epitaxially on a silicon wafer on the basis of an
example and a comparative example. The illustration shows in each
case the radial position P of five measurement points and the
associated resistivities R along the diameter of the silicon wafer.
The measurement points depicted in circular fashion represent a
silicon wafer in accordance with a comparative example which had
been coated in an apparatus without a spacer according to the
invention. The radial profile of the resistivity exhibits a
distinct asymmetry and falls significantly in the edge region of
the silicon wafer in comparison with the center region of the
silicon wafer. As shown by the measurement points depicted in
rhomboidal fashion, by contrast, the radial profile of the
resistivity of the epitaxially deposited layer of a semiconductor
wafer in accordance with the invention was almost symmetrical and
almost uniform. The silicon wafer in accordance with the invention
had been coated under the same process conditions as the silicon
wafer of the comparative example, but in an apparatus comprising a
spacer according to the invention.
FIG. 5 and FIG. 6 show the result of particle measurements that
were performed on silicon wafers with an epitaxially deposited
layer composed of silicon. The illustrations show maps which in
combination show the positions of particles that were detected by
scattered light measurements on, in each case, 25 silicon wafers
coated in accordance with the comparative example and the example.
The silicon wafers in accordance with the invention (FIG. 6) were
contaminated with particles to a significantly lesser extent and
exhibited no accumulation of particles in the edge region adjoining
the preheating ring like the silicon wafers of the comparative
example (FIG. 5).
While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
* * * * *